2009年9月26日 第5章_Memory extension.ppt

Chapter 5 :  Memory extension  &  I/O extension
Microcontroller Principle and Application
主讲教师:黄英
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Contents:
Memory extension introduction
Program memory extension
Chapter 5 Memory extension & I/O extension
Data memory extension
I/O extension introduction
I/O interface chip: 8255
Keyboard interface
LED Displayer interface
Home work (1)
Home work (2)
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Memory extension introduction
System extension & its structure
Memory extension & addresses arrangement
Contents:
Return
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System extension and it’s structure
1. Structure of system extension
2. System Bus & its construction method
Contents:
Return
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· Extension objects: ROM, RAM, I/O interface circuit, etc.
Fig. 1 The structure of system extension
1. Structure of system extension
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· In order to realize system extension, the first thing is:
to construct system bus
Return
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2. System Bus & its construction method
(1)System Bus
· System Bus is divided into three groups:
AB、DB、CB
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① Address Bus(AB)
· Carry address information.
· Single direction: MCU → Memory, I/O interface
· Its number determines the number of memory cells:
· Maximal extension space:
n → 2n
216 cells = 64KB
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② Data Bus(DB)
· Carry data information
· Bi-direction: MCU  Memory, I/O interface
· Bit number:
Word number(8 bits)
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③ Control Bus(CB)
· Carry control information
· Bi-direction :
MCU → Memory, I/O interface
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